Victor Duchovni wrote:
On Fri, Feb 06, 2009 at 09:11:43AM -0800, Roderick A. Anderson wrote:
mx.trendargentina.com.ar. 0 IN A 10.0.0.208
mx.trendargentina.com.ar. 0 IN A 10.0.0.207
What this says to me is every time Postfix requests the MX for
trendargentina.com.ar the name server software will look it up and come
back with _either_ 10.0.0.208 or 10.0.0.207 and depending on how many
other DNS requests are made it might be the same over and over.
No, this is wrong. Postfix shuffles MX host A records of equal priority.
OK. Obviously we're talking Postfix and after looking at the initial
post again I'm assuming the Exchange servers are on the local network
(10.0.0.x) so this makes sense.
Out in the wild with non-postfix/exim/sendmail mail servers requesting
MX records (because I wear several other hats including DNS admin) I'll
stick with equal priority/weight MX records.
Thanks,
Rod
--
If your zone file had
trendargentina.com.ar. 0 IN MX 10 mx1.trendargentina.com.ar.
trendargentina.com.ar. 0 IN MX 10 mx2.trendargentina.com.ar.
...
mx1.trendargentina.com.ar. 0 IN A 10.0.0.208
mx2.trendargentina.com.ar. 0 IN A 10.0.0.207
Then when Postfix asked for the MX record for trendargentina.com.ar the DNS
server would send back the two IP addresses and Postfix would
round-robin/randomize them.
This is wrong, see above.
I got the DNS info from readings in "Pro DNS and bind" and the Postfix from
this list and the online documentation.
You implementation has DNS doing the round-robin with the results depending
on how busy the name server is. Mine lets Postfix do it with a single
query to the name server.
Postfix does not rely on DNS servers shuffling the MX or A RRsets.
